OBJECTIVE To localize in normal monkey eyes the enzyme involved in the synsthesis of nitric oxide RESULTS NADPH-diaphorase is widespread in monkey eyes indicating significant nitric oxide production in various ocular structures DISCUSSION Frozen sections of the eyes were mounted on slides, then fixed with 4% paraformaldehyde. NADPH diaphorase histochemistry was performed using nitroblue tetrazolium. Staining was found in the anterior and posterior ocular segment. In the anterior segment, reaction product was present in the corneal epithelium and endothelium, iris dilator and sphincter, lens capsule, ciliary muscle and non-pigmented epithelial cells and stroma of the ciliary processes. Trabecular meshwork staining was minimal if at all. In the posterior segment, staining was seen around choroidal blood vessels and choroidal nerves, and in the retinal pigmented epithelial, photoreceptor, bipolar, inner plexiform and ganglion cell layers FUTURE DIRECTIONS The role of nitric oxide in the normal physiology of aqueous humor formation and drainage and the pathophysiology of glaucoma will be studied. KEY WORDS nitric oxide, trabecular meshwork, ciliary muscle, ciliary processes FUNDING NEI EY02698, GRF PUBLICATIONS Chen Z, Gu Q, Kaufman PL, Cynader MS Histochemical mapping of NADPH-diaphorase in monkey and human eye. Curr Eye Res 17:370-379, 1998. [J]